This invention relates to the processing of oat grain for conversion to a food product or to an intermediate product for further processing into a food product. In particular, it is directed to improved methods and apparatus to provide a toast flavor through enhancement of Maillard reactions in the groats while incurring a minimum of lipid oxidation and products to be made by the methods.
The Maillard reaction takes place when food components like reducing sugars and amino acids react together. This reaction occurs in most foods on heating. Maillard reaction chemistry can affect desirable flavors and color of a wide range of foods and beverages including malts and beers, bread, snacks, coffee, heated fruit and vegetable products, breakfast cereals, and meat.
One problem with efforts to enhance toast flavor in oat groats or their derivatives such as cut groats, bumped groats, flour, dough, flakes, etc., via Maillard reactions is the coincidental oxidation of lipids naturally contained in significant quantities in oat grain. The oxidized lipids can cause undesired off-flavor and rancidity.
Lipid oxidation can be initiated by the same thermal energy employed to activate and drive Maillard reactions to produce reaction products imparting favorable flavors. Once initiated, the lipid oxidation becomes autocatalytic and cannot be controlled easily, if at all. Complicating matters, oat groats contain natural enzymes which must be deactivated to stabilize the groat (or its derivatives) composition from degradation by the enzymes.
Conventionally, groats are tempered with steam to deactivate the enzymes, at least in part. A typical steam tempering process ranges from 12 to 15 minutes where the temperature of the groat reaches 210-220xc2x0 F. The tempered groats are then processed through a kiln where they are subjected to more heat, typically ranging up to 240xc2x0 F. During this kilning process the groats remain in a relatively high humidity (steam) atmosphere.
This process is generally successful at deactivating enzymes, avoiding rancidity, and producing a xe2x80x9ccookedxe2x80x9d flavor. However, the process is time and energy intensive and produces only a minimal toast flavor. Conventional kiln equipment also takes up substantial space and poses a relatively large capital expenditure.
Also an imposing problem is the obstructive morphology of the oat grain (or groat) itself. It appears that it is not well understood how to optimize Maillard reaction chemistry within the oat groat cellular structure itself, that is, in situ.
Accordingly, in an attempt to provide a successful enhancement of toast flavor to a final oat food product, others have conventionally shifted their focus from the difficult problem posed by the groat""s natural morphology to its more accessible derivative forms, down-stream of the groat pre-processing. For example, U.S. Pat. No. 4,963,373 issued to Fan et.al. discloses a toasting step involving oat flour dough, after a flaking process for a ready to eat (xe2x80x9cRTExe2x80x9d) cereal product. To prevent lipid oxidation during attempts to enhance toast flavor, many conventional methods rely on the addition of antioxidants such as BHA and BHT, before or after toasting to retard oxidation of the lipids.
None of these prior approaches provides a solution for dealing with enhancement of toast flavor in the gross cellular structure of either whole groats or split, cut, cracked, bumped, or flattened groats. Such forms of the oat groat are desired in consumer cooking as a main constituent to make, for example, an oatmeal porridge or an oatmeal cookie. They are also used in popular pre-prepared consumer products such as cereal bars, snack bars, textural coatings, etc., where the oats either provide an adjunct enhancement to flavor and texture of the product or serve as a main constituent of the product.
Recently, however, others have attempted improvements in adding toast flavor during an initial processing (or pre-processing) of oat groats. In particular, U.S. Pat. No. 5,523,109, issued to Hellweg et. al. discloses a method where xe2x80x9cwhole oat groats are steamed for greater times, dry toasted for extended timesxe2x80x9d in an attempt to provide a toasted oat flour after milling of the groat. Hellweg et. al. states that xe2x80x9cminimal peroxidase activity and a ratio of the HPLC syringic acid peak to ferulic acid peak, of about xe2x89xa72.5 which ratio is characteristic of a toasted flavor attribute.xe2x80x9d However, neither Syringic/Ferulic acids, nor phenolic acids in general, are believed by the present inventors to accurately reflect the formation of desired Maillard reaction products. Hence, the degree of success of this process is in doubt, or at least is not demonstrated.
The Hellweg et. al. process also suffers two further drawbacks. First, it employs steps which are energy and time intensive, in particular xe2x80x9csteaming for greater timesxe2x80x9d and dry toasting for xe2x80x9cextended times.xe2x80x9d Kilning is also included between the steaming and dry toasting step. This is not only a disadvantage in cost and manufacturing efficiency, but it also exposes the groat to extensive thermal energy, risking the initiation of autocatalytic oxidation of the lipids.
Second, the Hellweg et. al. process has a goal, to partially gelatinize or precook the groat. (See Hellweg et. al. reference to Farinograph measurements). This precooking and or partial gelatinization is not necessarily desirable when the groat is to be used in its integral or near-integral form; for example, as a cut groat, or rolled oat for consumer cooking into a porrige, or as either a whole groat or rolled groat as might be used in a granola or snack/cereal bar as an enhancing texturizer or as a main constituent.
In addressing these problems, the present inventors examined the unique attributes and constraints associated with whole oat groats and the Maillard reactions thought to be of interest for providing a toast flavor. Most notable is the constraint on reaction kinetics presented by the three dimensional morphology presented by the biological and cellular make up of a groat.
Also considered were the Maillard reactions themselves in terms of optimizing production of favorable products by providing conditions favorable to desired reaction paths occurring in the three basic phases of the Maillard reactions. In particular, the initial reactions (xe2x80x9cPhase I Maillard reactionsxe2x80x9d) are condensations of amino acids with simple sugars, in which each loses a molecule of water to form N-substituted aldosylamines. These are unstable and undergo Amadori rearrangement to form 1-amino-1-deoxy-2-ketoses, also known as xe2x80x9cketosamines.xe2x80x9d
These ketosamines can then undergo complex subsequent reaction paths toward Phase III products, generally characterized as either: (1) dehydration; (2) fission; or, (3) polymerization, reactions (xe2x80x9cPhase II Maillard reactionsxe2x80x9d).
The first Phase II path is simply for the ketosamines to further dehydrate (i.e., lose two water molecules) into reductones and dehydro reductones. Reductones and dehydro reductones, in their reduced state, are powerful antioxidants.
The second Phase II path produces short chain hydrolytic fission products, such as, diacetyl acetol, pyruvaldehyde etc.
In a third path from Phase II products to Phase III products, polymerization occurs to yield furfural and melanoids.
It is a goal of the present invention to at least enhance the second path of Phase II, so as to ultimately produce favorable nitrogen hetrocycles, in particular, pyrazines and thiazoles (Phase III Maillard products).
Due to the morphology of the oat grain (or groat), it was proposed that the simple sugars are constrained to an appreciable degree from physical molecular movement within the groat and, hence, are limited in their opportunity to come into contact with amino acids for reaction. To address this, it was proposed to increase the mobility of these simple sugars (i.e. mono, di, tri, and tetra, saccharides) by solubilizing them within the groat. Solubilization, it was believed, might be accomplished in significant degree by adding sufficient moisture to the groat. The amount of moisture necessary for this solubilization was then examined experimentally, as discussed below, although it was initially believed that between 1.5 to 2.0 times the normal amount of moisture contained in the groat may suffice, i.e. 21-30%.
It was also proposed that because dehydration reactions are a desired Phase II path, after mobilization of the simple sugars and/or amino acids, physical dehydration of this added moisture may help drive Phase II reaction equilibrium in a favorable direction.
Based upon experimental data, it is believed that unique process parameters have been determined resulting in improved processes for treating oat groats, cut groats, split groats, rolled groats, bumped groats or the like (xe2x80x9cgroatxe2x80x9d).
According to a first aspect of the invention, processes are directed to increasing the solution mobility, solution concentration, and/or solution kinetics with respect to at least simple sugars (ideally-mono, di, tri and tetra, saccharides) and amino acids within the groat. These all essentially will increase the availability of at least the simple sugars to react with nitrogen containing compounds, in particular amino acids. While it is a goal to increase the availability of at least the lower molecular weight sugars, it is also contemplated that higher molecular weight sugars such as tetrasaccharides may be made advantageously more available for reaction according to the invention.
A preferred method of increasing the availability is to increase the moisture content of the groat above its native or initial amount of water to a level sufficient to solubilize at least a sufficient amount of at least simple sugars present in the groat to yield a total concentration of selected Maillard reaction products (xe2x80x9cMRPxe2x80x9d) to about xe2x89xa734 ppb, after drying. Preferably, the moisture content is increased to above about 14%, but more preferably above 18-20% by weight.
Another proposed method for increasing the availability via increasing solution kinetics is to direct microwave energy into a moist groat. Advantageously, this method can also be enhanced by increasing the moisture content of the groats as noted above. Synergistically, heat generated by the microwaves can supply necessary activation energy for the desired Maillard reactions.
According to a separate aspect of the invention, a unique method of controlling the thermal history of a groat, at least during Maillard reaction, was found to be beneficial. It was noted that during conventional processes, in particular kilning, the ambient environment surrounding each groat includes high heat and humidity (e.g. as imparted by steam vapor). It was also noted that Maillard reactions are exothermic and thus necessarily generate heat within the groat. It was also proposed that due both to this conventional kilning environment and the groat""s cellular morphology, heat transfer from the groat may be excessively restricted. This may provide for inadequate control of the reaction process temperatures occurring in situ. In other words, groats in such a conventional environment are intended to be equilibrated to the imposed environmental temperature. However, it would appear that it has heretofore not been taken into account that a groat brought up to the imposed environmental temperature will generate internal thermal energy which, if not dissipated, will cause an internal groat temperature higher than the thermally buffered environment. In such a case, the internal temperature of an individual groat may become excessive with respect to avoidance of lipid oxidation and with respect to formation of desirable Maillard products.
Accordingly, other methods according to the invention include providing more control over the thermal stability of each groat during processing. In general the invention contemplates enhancing the removal of thermal energy from the individual groats to better correlate the internal temperature of the groat with its controlled external environment. One way to accomplish this is to provide an atmosphere, such as air, about the groats with sufficiently low relative humidity to encourage evaporation of water from the groat thereby removing heat (of vaporization) from the groat during Maillard reactions. Moving this air, such as by a fan, may provide added control of thermal energy in the groat as the rate of evaporation can be better controlled.
A synergistic advantage of such thermal control is that the groats can be dried relatively rapidly compared to conventional processes, while still yielding as much or more desirable Maillard products in the groats. By providing heat to the air, especially the moving air, even more refined control can achieved. By varying the temperature, mass flow, and relative humidity of the drying atmosphere, a large degree of control is available. The heated air not only aids in evaporation, it can also provide the necessary activation energy needed while synergistically directing the groat toward a more isothermal internal temperature.
It should be understood that providing thermal energy sufficient to drive Maillard reactions and/or assist in evaporation may be supplied by other conventional means than heated air, such as infrared lamps. The importance of such thermal input being of primary significance, as opposed to its source.
Hence, preferred methods according to the invention may include increasing the moisture content of the groats and drying of the groats to an acceptable water content for storage in about 8-30 minutes. From an another approach, the reaction of simple sugars and dehydration or drying of the groat can be accomplished preferably at a rate of about 0.5-3% by weight moisture per minute.
Another process of the invention includes increasing the moisture content of the groats to xe2x89xa720% by weight and drying the groats with an atmosphere having a temperature of about 200xc2x0 F. Also, the moisture content of the groats can be increased to  greater than 15% and then successfully dried in about xe2x89xa660 minutes, preferably in the range of about 8-60 minutes. Another aspect of the invention is to increase the moisture content of the groats to  greater than 20% and then drying the groats for about 8-30 minutes. According to another aspect of the invention, the moisture content of the groats is increased to  greater than 14% by weight and then heated to reduce the moisture content at a rate of about 0.5-3% by weight moisture per minute.
According to preferred methods, it was found that oat groats with improved toast flavor having an MRP xe2x89xa7about 34 ppb and a ratio of MRP to a concentration of certain lipid oxidation products (xe2x80x9cLOPxe2x80x9d) which is xe2x89xa76.0/100 (in other words, (MRP/LOP)xc3x97100=6.0)) can be produced. Preferably, oat groats can be made according to the methods of the invention having an MRP value within a range of about 100 to 2300 ppb and a corresponding ((MRP/LOP)xc3x97100) value in the range of about 7-500 ppb.
It should also be understood that once the groats have developed the desired Maillard products, the flavors and or aromas imparted thereby should be present in post-processed (e.g. grinding, milling, etc.) or derivative forms (e.g. flour) of the groats.